1. Field of the Invention
The present invention relates to a pneumatic tire in which running performance on snowy roads can be improved while keeping steering stability, drainage performance and running performance on icy roads.
2. Description of the Related Art
In recent years, pneumatic tires for winter such as studless tires have a lot of chances to run not only snowy and icy roads but also dry and wet roads. Accordingly, such pneumatic tires for winter are required to improve not only running performance on snowy and icy roads but also steering stability and drainage performance in well-balanced manner.
Generally, in order to improve drainage performance and running performance on snowy roads, a tire with a tread portion provided with a main groove with a large width is proposed. Such tire can smoothly drain water and snow under the tread portion to the outside of the tire. On the other hand, the ground contact area in the tread portion of such tire tends to decrease due to the large width of the groove, and thereby pattern rigidity of the tread portion and friction force against roads may deteriorate. Accordingly, such tire tends to have low steering stability and low running performance on icy roads.
It is an object of the present invention to provide a pneumatic tire in which running performance on snowy roads can be improved while keeping steering stability, drainage performance and running performance on icy roads.